Color Filters and Shooting RAW

I'm brand new to both diving and underwater photography (although I'm a fairly experienced above-water photographer).

I'm curious about how shooting RAW effects the need for blue or green water filters while diving. When shooting with available light, do filters compensate/correct for more than what's possible from a RAW file in post-production? Are there people shooting without filters and doing corrections in post, or is it best to avoid that and shoot with the appropriate filter each time?

When i was shooting in ambient light, I always used to manual white balance as well.
Later on when processing I find it easier to make corrections. Using a filter will also need manual white balance. It's easier tot get the shot as good as possible, rather then processing it later on which will take down the quality a bit.

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Posted 22 March 2013 - 12:27 AM

As you probably know, the red light is absorbed fairly quickly underwater. Take a look at the RGB histogram of a picture shot in ambient light at some depth, and you'll see that the red channel is quite underexposed. At shallow depths, there's usually enough information in the red channel to restore it without unacceptable loss in image quality, but sometimes the red channel is so underexposed that restoring it is a bit of a challenge, and you'll get a lot of noise in the process.

If the red channel is severely underexposed, you can either increase exposure with the definite risk of burning out the blue and/or green channel, or you can put on a red filter, which effectively gives you the same effect (increasing exposure of the red channel), but without that risk of burning out the blues and/or greens. It comes at a cost, though: You have to use a larger aperture, a longer shutter speed or a higher ISO.

Of course, if you're deep enough that the red wavelengths are severely absorbed by the water, you'll need artificial lighting (e.g. a strobe) to get the true colors of the subject at depth. No filter can restore wavelengths that just aren't there.

Disclaimer: This is from a purely theoretical view and I haven't tried filters in practice. Yet. But I'm seriously considering that for available light shooting. For a more informed view from people with actual experience, you might like to read this and this article.

Bear in mind that a filter filters out light. A red filter stops (or reduces) cyan light passing and a yellow filter stops (or reduces) blue light passing. It cannot put back colour that is not there. So if you go deep enough that there is no long wavelength spectrum of light and that's not very deep at all (say 60ft) , all a filter will do is increase the exposure needed to get an image.

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Bear in mind that a filter filters out light. A red filter stops (or reduces) cyan light passing and a yellow filter stops (or reduces) blue light passing. It cannot put back colour that is not there. So if you go deep enough that there is no long wavelength spectrum of light and that's not very deep at all (say 60ft) , all a filter will do is increase the exposure needed to get an image.

I am rather unexperienced in underwater photography too just started but I am as experienced on land photographer as well...

Yes filters do take light away so it is not restoring anything, you have open apeature, higher iso or longer exposure. Shooting in raw without filter but decently exposed will give you the most information on a picture you can get and I am sure this is the way to get out the most you can... I recognized once you get to a point you know what to do in your RAW converter to get decent colors on your RAW pic it is fairly easy and took me only a few shots, though I am not an expert yet! It also gives me the opportunity to work on the picture style much more to get out of it what I want e.g. vibrant dark blue water...

I would always rather open 1 or 2 stop, go up one higher iso number... to get more red information on the RAW file than open 2 stops or... to compensate for light loss of the filter! In my opinion as long as you can get a shot with ambient light and filter you can do better with RAW and post processing as you got more picture information to work with.